Fluorine-containing polymers, or fluoropolymers, are an important class of polymers and include for example, amorphous fluorocarbon elastomers and semi-crystalline fluorocarbon plastics. Within this class are polymers of high thermal stability and usefulness at high temperatures, and extreme toughness and flexibility at very low temperatures. Many of these polymers are almost totally insoluble in a wide variety of organic solvents, and are chemically inert. Some have extremely low dielectric loss and high dielectric-strength, and most have unique nonadhesive and low-friction properties. See, for example, F. W. Billmeyer, Textbook of Polymer Science, 3rd ed., pp. 398-403, John Wiley & Sons, New York (1984).
Amorphous fluorocarbon elastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers, such as hexafluoropropene, have particular utility in high temperature applications, such as seals, gaskets, and linings--see, for example, Brullo, R. A., "Fluoroelastomer Rubber for Automotive Applications," Automotive Elastomer & Design, June 1985, "Fluoroelastomer Seal Up Automotive Future," Materials Engineering, October 1988, and W. M. Grootaert, G. H. Millet, and A. T. Worm, "Fluorocarbon Elastomers," Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 8, pp. 990-1005 (4th ed., John Wiley & Sons, 1993).
Semi-crystalline fluoroplastics, particularly polychlorotrifluoroethylene, polytetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, and poly(vinylidene fluoride), have numerous electrical, mechanical, and chemical applications. Fluoroplastics are useful, for example, in wire coatings, electrical components, seals, solid and lined pipes, and pyroelectric detectors. See, for example, "Organic Fluorine Compounds," Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 11, pp. 20, 21, 32, 33, 40, 41, 48, 50, 52, 62, 70, 71, John Wiley & Sons, (1980).
In spite of their many good properties, a drawback of most semi-crystalline fluoroplastics is their need for high processing temperatures. Since the decomposition temperatures of the fluoroplastics tend to be in the same range as the processing temperatures for many of these materials, corrosion-resistant equipment is required. Furthermore, the need for high processing temperatures prevents the co-processing of the fluoroplastics with other polymeric materials which are not thermally stable at such temperatures. When a multi-layer composition is desired, the materials must be processed sequentially or the fluoroplastics must be paired with high temperature resistant polymers which tend to be more expensive. Thus, there is a need in the art for semi-crystalline fluoroplastics which can be processed at lower temperatures and for one-step methods for preparing multi-layer compositions therefrom. There is also a need for multi-layer compositions which exhibit chemical resistance, barrier properties, low flammability, and good electrical properties for use in applications such as wire and cable insulation, hose constructions, electrical connections, and heat-shrink tubing.